Evolutionary Roots and the Miacids

Most of what truly happened during the evolution of bears will remain forever shrouded
in the mists of the distant past .....

From what we do know, however, we have been able to piece together that approximately
30 to 40 million years ago during the Oligocene period, a family of small, tree-climbing
carnivorous mammals came into being.

These animals, now referred to as miacids, had developed special canine teeth which
enabled them to pierce and tear the flesh of their prey. Additionally, the miacids had
developed sharp-edged carnassial teeth (i.e., the last premolar in the upper jaw) and the
first molar in the lower jaw. This development allowed the miacids to easily shear meat
from a carcass into easily eaten smaller chunks of meat.

From an evolutionary perspective, these two developments led to the miacids becoming
the precursor to all seven present carnivore families. Today, of the approximately 4500
mammals known to exist, 231 are classed as carnivores. All would become successful groups
of predators. Included in the carnivore families are the following:

the Canidae (dog) family - 35 species including the fox, wolf,
coyote and jackal;

the Procyonidae (raccoon) family - 16 species including the
ringtail, kinkajou and raccoon;

the Mustelidae (weasel) family - 67 species including badger,
otter and skunk;

the Viverridae (mongoose) family - 66 species including mongoose,
genet and meercat;

the Hyaenidae (hyena) family - 4 species including spotted hyena,
striped hyena, brown hyena and aardwolf;

the Felidae (cat) family - 35 species including leopard, cheetah
and mountain lion;

and

the Ursidae (bear) family - eight species including the brown
bear, the American black bear, the polar bear, the giant panda bear, the Asiatic black
bear, the spectacled bear, the sloth bear and the sun bear.

Evolutionary Roots of the Modern Bear

The first bears are known to have evolved from a heavy bear-like dog that developed
from the miacids. This animal is known to have existed sometime during the late Oligocene
period, some 27 million years ago.

We also know that approximately 20 million years ago in subtropical Europe, a bear
about the size of a small terrier existed. It is now referred to as Ursavis elemensis.

Approximately two and a half million years ago, the direct ancestors of our modern
bears appeared on the planet. Members of this genus named Ursus (Latin for bear) later
divided into three distinct evolutionary lines. Two of the lines were established in Asia
and it is thought that they led to what is now the brown bear and the black bears. The
third line developed in Europe.

From the European line of bears came the animal known as Ursus spelaus and often
referred to in the literature as the "cave bear". Arriving in Europe
approximately 30,000 to 40,000 years ago, they were a large mammal with large males
weighing in excess of 400 kilograms (880 pounds). It is believed that they hibernated much
as do our present bears and were opportunistic omnivores.

These bears appear to have both preyed upon and been the prey of our early human
ancestors. Prior to recorded history, these animals had become extinct. Today, the
European brown bear has taken over the habitat formerly occupied by the Ursus spelaus.

Another bear which has become extinct is Arctodus simus, commonly referred to as the
short-faced "bulldog" bear. With remains of this bear discovered in the tar pits
of southern California, it appears it arrived in North America via the Bering land bridge
that at one time linked North America to Asia.

This bear, possibly the largest bear that ever existed, was significantly larger than
the present day Kodiak brown bears of Alaska. It had exceptionally long legs adapted to
swift pursuit of prey. It appears to have been very fierce and highly predatory in nature.

The "bulldog" bear disappeared approximately 12,000 years ago in the same
time period which saw the extinction of mammoths, sabre-toothed cats and many other large
mammals. Its habitat since has been taken over by the brown bear.